Water contaminated with salts over 1,000 parts per million (ppm) is not fit for human consumption. There are many known processes for separating ions and other dissolved solids from water but most of them require large amounts of energy and extensive knowledge to operate. Examples include distillation, reverse osmosis, ion exchange and electrodialysis.
Capacitive deionization is another process used to separate ions from an ionic fluid. This method typically employs two electrodes with spaced-apart end plates in a cell. As the ionic fluid enters the cell, it flows through a channel defined by the electrodes, substantially parallel to the electrodes. By polarizing the cell by energizing the electrodes, ions are removed from the ionic fluid and are held on the surface of the electrodes. Once the cell is saturated with the removed ions, the cell is regenerated by discharging the electrodes and releasing the ions held at the electrodes. In a typical setup, an output pipe is closed with a valve prior to regeneration and the flow is redirected to an alternate waste conduit. Once a sufficient amount of ions are released, the system is deemed to be regenerated. At that point the operator can recommence the deionization process by closing the valve to the waste conduit, recharging the electrodes, and reopening the valve to the output pipe.
Through the use of microscale technology, capacitive deionization can be applied to reduce energy concerns and implement such systems on a more large-scale basis. Electric fields are effective at pulling charged particles through a medium over short distances, and microtechnology allows for these small distances to be used in conjunction with electric fields to efficiently remove ions from water and produce a clean flow of water that can be collected for subsequent use. Since an electric field is produced by a voltage gradient, it is possible to create high voltage potentials without requiring large currents which results in a low power usage.